Land and climate effects of bioenergy - Brazilian sugarcane ethanol and combined biofuel-district heating in Europe
Doctoral thesis, 2016
According to the Intergovernmental Panel on Climate Change, use of fossil fuels is the largest source of
the increase in atmospheric CO2. The second largest is land use change. To reach stringent climate targets,
emissions from fossil fuel combustion and land use change will need to be reduced to near zero
within a few decades. Biomass is a renewable energy source that can be used to replace fossil fuels.
However, it is a limited resource, expected to become scarce relative to future demand, prompting interest
in optimizing efficiency. Further, when biomass for biofuels expands into new land areas, the total
biospheric carbon stock (the sum of soil and above-ground carbon) may increase or decrease, influencing
the net effect on greenhouse gas balances. This thesis, which consists of five separate papers, analyzes
several key aspects associated with two bioenergy systems: (i) combined biofuels and district heat production
in the EU and (ii) sugarcane for ethanol production in Brazil, with special attention to integration
with existing food and energy systems. The overall aim is to investigate specific options for improving
management of land use and land use change, efficient use of resources, and greenhouse gas balances for
specific bioenergy systems.
In Paper I, we study biomass gasification for the production of biofuels and heat for district heating systems
in Europe. We find that each investigated country, except Italy, has a heat sink capacity in its district
heating systems that is larger than the amount of heat that would be co-generated in plants producing
biofuel volumes corresponding to national biofuel targets.
In Papers II–V, we study expansion of sugarcane ethanol production in Brazil at the regional, state, and
national levels, including both conventional sugarcane ethanol systems and combined ethanol-milk production
systems in which sugarcane residues are used as animal feed. We find that the harvest method
influences greenhouse gas emissions from sugarcane-based ethanol production, as does the impact on
soil carbon content. How the by-product bagasse is used also affects the results.
For Paper V, we interview Brazilian farmers and landholders regarding their actions connected to engaging
with sugarcane production. We find that it is common among the interviewees to invest profits from
sugarcane production to maintain and improve the prior beef and milk production systems. This likely
affects indirect land use change associated with sugarcane expansion on former pasture land.
biofuels for transport